This invention relates generally to cartridges for medical solutions, but more particularly to a cartridge of the type adapted for use in storing and dispensing narcotics. Presently, cartridges containing narcotics for medical use have no effective safe-guards to prevent dilution of the contents, not a means for indicating the amount of original solution in the cartridge that has been withdrawn. Consequently, a large portion of the narcotic solutions administered in the course of patient therapy has been diluted by the personnel in our institutions and professional offices. Therefore, many patients suffer severely as a result of receiving less than the prescribed dosages of pain depressants, and accordingly pay for medications which are never administered to them. For this reason, the applicant has designed a cartridge which will accurately indicate the amount of original solution which has been withdrawn.